For much of history, the mark of an enviable woman has been her ability to secure a superior match, through her beauty, cleverness, or artful deception. After civil rights, that expectation mellowed into something called “homogamy,” meaning women marrying men of equal money and education. But that happy place of equilibrium seems to be fading as well. Instead, women have started doing something demographers thought they would never see: they are marrying down, not just in the United States but all over the world, a phenomenon closely tracked by Spanish demographer Albert Esteve.

Women are largely doing this out of necessity. In every continent except Africa, women are more likely to have a college degree than the men around them. This means that in their late 20s and 30s, when most people get married, women’s earning prospects are brighter. So they have no choice but to marry someone who in a Jane Austen novel would have been declared an unsuitable match. About 40 percent of wives in the United States now out-earn their husbands, and researcher Liza Mundy predicts they will be the majority in a generation. It’s already happening with education: According to Esteve, the majority of women in France, Hungary, Israel, Portugal, Brazil, Belarus, Mongolia, and Colombia—to name a few—now marry men with less schooling than they have.